5 March 2013

New evidence that comets may have seeded life on Earth

by Will Parker

A new experiment simulating conditions in deep space has shown that linked pairs of amino acids - essential building blocks shared by all living things - could have been created on icy interplanetary dust and then carried to Earth where they jump-started life. Details of the experiment are reported in The Astrophysical Journal.

The discovery, by chemists from the University of California - Berkeley and the University of Hawaii, opens the door to the possibility that these molecules were brought to Earth aboard a comet or possibly meteorites, catalyzing the formation of proteins (polypeptides), enzymes and even more complex molecules, such as sugars.

While scientists have previously discovered basic organic molecules, such as amino acids, in numerous meteorites that have fallen to Earth, they have been unable to find the more complex molecular structures that are prerequisites for our planet's biology. As a result, scientists had previously assumed that the really complicated chemistry of life must have originated in Earth's early oceans.

In the new experiment, a vacuum chamber chilled to 10 degrees above absolute zero was used to house a mix of ice, carbon dioxide, ammonia, and various hydrocarbons such as methane, ethane, and propane. When zapped with high-energy electrons to simulate cosmic rays in space, the chemicals reacted to form complex, organic compounds.

Specifically, the researchers witnessed the creation of dipeptides (linked pairs of amino acids), which are essential to life on Earth. Further analysis revealed the presence of nine different amino acids and at least two dipeptides, which the researchers say are capable of catalyzing biological evolution on Earth.

"It is fascinating to consider that the most basic biochemical building blocks that led to life on Earth may well have had an extraterrestrial origin," concluded UC Berkeley chemist and study co-author Richard Mathies.